Analyst Blog

LED-SERDS in Raman Spectroscopy

Raman spectroscopy finds a range of uses in analytical chemistry. Like infra-red (IR) spectroscopy it can provide a vibrational fingerprint by which compounds may be identified. Unlike IR, Raman is a scattering technique that does not require complex sample preparation, and water can be used as a solvent. In some samples, however, the Raman spectrum is rendered useless by intense fluorescence signals.

Chemical engineers Renata Adami (University of Salerno, Italy) and Johannes Kiefer (University of Aberdeen, UK) have developed a new approach to shifted-excitation Raman difference spectroscopy (SERDS) for suppression of fluorescence. SERDS experiments conventionally require expensive diode lasers, but in this Analyst paper Kiefer and Adami demonstrate the use of light-emitting diodes (LEDs) as an inexpensive light source. A dielectric bandpass filter narrows and stabilises the broad LED spectrum to make it usable for SERDS. While the resulting spectral resolution is low, different compounds and functional groups can be clearly distinguished using this method.

To read the full access, please click on the link below. This paper will be free to read for the next three weeks:

Low cost webcam based prism spectrometer

Techniques such as cavity ring-down spectroscopy (CRDS) have greatly enhanced the sensitivity in traditional absorption spectroscopy methods. Although CRDS can detect analytes in very small concentrations in solution, it requires expensive and complex instrumentation, which has restricted its widespread implementation. Alternatively, broadband cavity enhanced absorption spectroscopy (BBCEAS) has emerged to overcome some of these limitations. These adjustments allow for multiplexed data collection and improved resolution.

Researchers at the University of Cambridge, UK,  have constructed a BBCEAS apparatus using relatively simple components and achieved sensitivity levels similar to much more expensive systems.  Using a well-studied process, the Griess Assay, they measured different concentrations of nitrite and the dye Rhodamine 6 G with a system that contained a low cost prism spectrometer and a webcam detector. The limits of detection were found to be 3.7 nM (nitrite) and 850 pM (Rhodamine), and by adding a better detector, these can further be improved upon.

To read the full article, please access the link below. This paper will be free to read for the next three weeks:

High sensitivity liquid phase measurements using broadband cavity enhanced absorption spectroscopy (BBCEAS) featuring a low cost webcam based prism spectrometer
Zhechao Qu, Julia Engstrom, Donald Wong, Meez Islam and   Clemens F. Kaminski
Analyst, 2013,138, 6372-6379
DOI: 10.1039/C3AN01441J

Analysis of intracellular enzyme activity by SERS

Enzymatic activity in cells has been revealed by surface enhanced Raman scattering (SERRS) spectroscopic studies, according to new research led by Duncan Graham at the University of Strathclyde.

X-Gal, a SERRS inactive precursor and a common marker for galactosidase enzymes, was introduced to macrophage cells along with metal nanoparticles. On incubation, enzymatic activity of galactosidase on X-Gal produces a SERRS active trans-alkene dimerised product. This product adsorbs onto the delivered citrate capped gold nanoparticles producing a distinctive SERRS signal. Using SERRS mapping to evaluate the formation of this product, enzyme activity was assessed, not only across a cell population, but also at sub-cellular levels. The authors note that the SERRS activity in this study may not reflect the only sites of galactosidase activity, but rather the sites where both galactosidase and the nanoparticles are co-located. Nevertheless, approaches towards sub-cellular analysis of enzyme activity are important.

Advances in targeted nanoparticle uptake combined with the multiplexing capability of SERRS make this an interesting approach to sub-cellular studies of biochemical activity.

To read the full article, please click on the link below. This paper will be free to read until October 18th.

Analysis of intracellular enzyme activity by surface enhanced Raman scattering
Ross Stevenson, Sarah McAughtrie, Laura Senior, Robert J. Stokes, Helen McGachy, Laurence Tetley, Paola Nativo, James M. Brewer, James Alexander, Karen Faulds and   Duncan Graham
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN00729D

Take a look at these new HOT articles just published in Analyst! These papers will be free to read for the next three weeks. Download them today!

The global identification of tRNA isoacceptors by targeted tandem mass spectrometry
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DOI: 10.1039/C3AN01224G

Extraction and separation of proteins by ionic liquid aqueous two-phase system
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A smart T1-weighted MRI contrast agent for uranyl cations based on a DNAzyme–gadolinium conjugate
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Improved analysis of oligosaccharides for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using aminopyrazine as a derivatization reagent and a co-matrix
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A chemical quenching- and physical blocking-based method to minimize process-mediated aggregation of antibody-crosslinked nanoparticles for imaging application
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Exploring the electrochemical performance of graphitic paste electrodes: graphene vs. graphite
Luiz C. S. Figueiredo-Filho, Dale A. C. Brownson, Maria Gómez-Mingot, Jesús Iniesta, Orlando Fatibello-Filho and Craig E. Banks  
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An investigation into the simultaneous enzymatic and SERRS properties of silver nanoparticles
Kristy S. McKeating, Sian Sloan-Dennison, Duncan Graham and Karen Faulds  
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01451G

Electrochemical piezoelectric-excited millimeter-sized cantilever (ePEMC) for simultaneous dual transduction biosensing
Blake N. Johnson and Raj Mutharasan  
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01353G

Take a look at these new HOT articles just published in Analyst! These papers will be free to read for the next two weeks. Click on the links below:

A new turn-on fluorescent chemosensor based on diketopyrrolopyrrole (DPP) for imaging Zn²⁺ in living cells
Guanjun Zhang, Haiying Li, Shiming Bi, Longfeng Song, Yunxiang Lu, Liang Zhang, Jianjun Yu and Limin Wang  
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN00873H

Separation of metalloproteins using a novel metal ion contaminant sweeping technique and detection of protein-bound copper by a metal ion probe in polyacrylamide gel electrophoresis: distribution of copper in human serum
Shingo Saito, Mitsuyoshi Kawashima, Hiroki Ohshima, Kazuki Enomoto, Makoto Sato, Hajime Yoshimura, Keitaro Yoshimoto, Mizuo Maedad and Masami Shibukawaa  
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High pressure nanoelectrospray ionization mass spectrometry for analysis of aqueous solutions
Md. Matiur Rahman, Mridul Kanti Mandal, Kenzo Hiraoka and Lee Chuin Chen 
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Introducing novel amorphous carbon nanoparticles as energy acceptors into a chemiluminescence resonance energy transfer immunoassay system
Zhenxing Wang, Hongfei Gao and Zhifeng Fu 
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DOI: 10.1039/C3AN01177A

The global identification of tRNA isoacceptors by targeted tandem mass spectrometry
Collin Wetzel and Patrick A. Limbach 
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Enhanced imaging of developed fingerprints using mass spectrometry imaging
M. J. Bailey, M. Ismail, S. Bleay, N. Bright, M. Levin Elad, Y. Cohen, B. Geller, D. Everson, C. Costa, R. P. Webb, J. F. Watts and M. de Puit  
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DOI: 10.1039/C3AN01204B

Photonic crystal enhanced microscopy for imaging of live cell adhesion
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Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01541F

Ultrasensitive electrochemical detection of leukemia cells

Detecting cancerous cells, such as those of leukemia, in early stages can greatly affect patient treatment and survival. Current diagnostic tools such as immunohistochemistry require large concentrations of cells, which occur in advanced stages of the disease.

Jun-Jie Zhu and co-workers at Nanjing University , China, developed an assay for leukemia cells using aptamers in a unique, competition-based electrochemical sensor. This involves the use of magnetic (Fe3O4) and gold nanoparticles and the detection of electrochemical signals from deposited silver nanoparticles using square wave anodic stripping voltammetery. The gold nanoparticles bind to the much larger magnetic particles through an apatmer, but the apatmer has a higher specificity for the leukemia cells. Upon introduction of the cells, some of the gold nanoparticles are released from the magnetic surface affecting the amount of detectable signal from the silver. The researchers successfully detected as few as 10 cells and demonstrated a high specificity of the aptamers for only one type of leukemia cells. Although they chose leukemia cells, the only limitation is the specificity of aptamers available and ideally, any cancer could be tested for in this system.

To read the full article, please access the link below. This paper will be free to read for the next three weeks.

A novel aptamer-based competition strategy for ultrasensitive electrochemical detection of leukemia cells
Kui Zhang, Tingting Tan, Jia-Ju Fu, Tingting Zheng and   Jun-Jie Zhu
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01255G

Detection of E. coli in Ringer's solution

Sophisticated analytical tests producing a readout which can be interpreted by the naked eye, or by image editing software, are becoming increasingly popular.  They offer a low cost alternative to tests requiring expensive equipment and highly trained analysts. Jürgen Popp and colleagues from the Friedrich Schiller University and the Institute of Photonic Technology in Jena, Germany, have developed a new detection method for DNA which provides a distinctive colour change in the case of a positive result.

The bacterial contamination of intravenous fluids in hospitals is a significant concern in modern medicine, so Popp and his team chose the detection of E. Coli in Ringer’s solution as the first test for their assay. The technique uses surface-modified magnetic beads which can bind complementary target DNA by hybridisation. A silver deposition kit provides the visual colour change: for a positive result, silver nanoparticles are generated by enzymatic silver deposition, turning the sample black. As well as being an inexpensive and convenient qualitative test, a quantitative result can be found by analysing a digital photograph of the colour change in standard image editing software.

To read the full article, please cick on the link below. The paper will be free to read for the next three weeks.

Convenient detection of E. coli in Ringer’s solution
Martha Schwarz, Susanne Pahlow, Thomas Bocklitz, Carolin Steinbrücker, Dana Cialla, Karina Weber and Jürgen Popp
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01240A

BODIPY-Based Probe for HClO Imaging

Detection of suitable biomarkers of disease is critical for medical diagnosis. However, detection becomes a paradoxical challenge when the biomarker is naturally found in healthy individuals. This is the case for the biomarker hypochlorous acid (HClO), a reactive oxygen species that plays an essential role in maintaining a healthy immune system under normal conditions. Yet, when optimal levels of HClO cannot be maintained by the body, cellular functions become disrupted and this can result in diseases such as atherosclerosis, arthritis, and cancer. Consequently, HClO requires medical monitoring, particularly in the mitochondria where a high concentration tends to reside. To help distinguish between healthy and diseased states, the ideal biosensor must provide fast response, high selectivity, high sensitivity and mitochondrial permeability.

To address this challenge, Xiaojun Peng and colleagues from the Dalian University of Technology in China have created a fluorescent imaging probe to detect HClO by localizing to mitochondria in live cells. Their probe makes use of boron dipyrromethene (BODIPY) dye for its outstanding fluorescent properties. Incorporation of an oxime group onto the BODIPY scaffold allows the tuning of fluorescence to an on/off state depending on the presence/absence of HClO, respectively. Lastly, incorporation of a triphenylphosphine group onto BODIPY provides the localization signal to the mitochondria. Learn all the details of this exciting new discovery by accessing the link below:

A highly specific BODIPY-based probe localized in mitochondria for HClO imaging
Guanghui Cheng, Jiangli Fan, Wen Sun, Kun Sui, Xin Jin, Jingyun Wang and   Xiaojun Peng  
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01152F

This pap[er will be free to read for the next three weeks. Let us know what your thoughts are by leaving a comment!

Check out the latest HOT articles just published in Analyst! They are all free for you to read for the next three weeks. Enjoy!

A protein nanofiber hydrogel for sensitive immunoassays
Dae-Sung Lee, Jin-Seung Park, Eun Jung Lee, Hyun Jin Kim and Jeewon Lee
Analyst, 2013,138, 4786-4794
DOI: 10.1039/C3AN00564J

Anodic stripping voltammetric determination of cadmium using a “mercury free” indium film electrode
Sukeri Anandhakumar, Jayaraman Mathiyarasu and Kanala Lakshimi Narasimha Phani
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01070H

Alteration of Asian lacquer: in-depth insight using a physico-chemical multiscale approach
Anne-Solenn Le Hô, Chloé Duhamel, Céline Daher, Ludovic Bellot-Gurlet, Céline Paris, Martine Regert, Michel Sablier, Guilhem André, Jean-Paul Desrochese and   Paul Dumasf
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Luminescence lifetime-based capillary oxygen sensor utilizing monolithically integrated organic photodiodes
Bernhard Lamprecht,  Andreas Tschepp, Merima Cajlakovic, Martin Sagmeister, Volker Ribitsch and Stefan Köstler
Analyst, 2013, Accepted Manuscript
DOI: 10.1039/C3AN00208J

Dual detection of cancer biomarker CA125 using absorbance and electrochemical methods
Israa Al-Ogaidi, Zoraida P. Aguilar, Savan Suri, Honglei Gou and Nianqiang Wu
Analyst, 2013, Advance Article
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Desorption electro-flow focusing ionization of explosives and narcotics for ambient pressure mass spectrometry
Thomas P. Forbes, Tim M. Brewer and Greg Gillen
Analyst, 2013, Advance Article
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High-throughput analysis of drugs in biological fluids by desorption electrospray ionization mass spectrometry coupled with thin liquid membrane extraction Cecilie Rosting, Stig Pedersen-Bjergaard, Steen Honoré Hansen and Christian Janfelt
Analyst, 2013, Advance Article
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Multifunctional carbon nanoelectrodes fabricated by focused ion beam milling
Rahul Thakar, Anna E. Weber, Celeste A. Morris and Lane A. Baker
Analyst, 2013, Advance Article
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Facile synthesis of quantum dots/mesoporous silica/quantum dots core/shell/shell hybrid microspheres for ratiometric fluorescence detection of 5-fluorouracil in human serum
Rijun Gui, Ajun Wan and Hui Jin
Analyst, 2013, Advance Article
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Optimization of microfluidic PET tracer synthesis with Cerenkov imaging
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Analyst, 2013, Advance Article
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A label-free and colorimetric turn-on assay for coralyne based on coralyne-induced formation of peroxidase-mimicking split DNAzyme
Ting Hou, Xiuzhong Wang, Xiaojuan Liu, Shufeng Liu, Zongfeng Du and Feng Li
Analyst, 2013,138, 4728-4731
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Rapid detection and identification of bacteria in sepsis

Infections of the blood are a major cause of death, even in countries where antibiotics are widely available. A large hurdle to successful treatment of this type of infection is the identification of the responsible bacteria, which can take several days. Clinicians often resort to the use of broad spectrum antibiotics, which encourages the rise of antibiotic resistant bacteria in the population.

In this collaborative work, researchers led by James Carey at the National University of Kaohsiung, Taiwan, and David Engebretson of Oklahoma City University in the United States, report the design and testing of a colorimetric sensor for bacterial identification. The process simultaneously cultures the bacteria and analyses the unique fingerprint of gases and metabolites produced. The single-step testing kit is automated and disposable, unlike current methods which require skilled technicians, and is so far able to distinguish between eight of the most common pathogens.

By combining the detection and identification of bacteria, the authors are confident that this new technology will prove to be a major step forward in the treatment and outcome of sepsis in patients.

To read the full paper, free for you for the next three weeks, please access the link below:

Single step, rapid identification of pathogenic microorganisms in a culture bottle
Yu W. Chu, Bo Y. Wang, David A. Engebretson and   James R. Carey
Analyst, 2013, Advance Article
DOI: 10.1039/C3AN01175E